Or, why am I relatively unconcerned about dandelions in my lawn, and yet very upset about invasive species taking over woods and meadows throughout our region?
A weed is simply an undesirable plant: a plant that is growing in the wrong place. Most likely the plant is unwanted because it grows too aggressively, is unattractive, or has some other negative impact on the landscape or ecology.
Dandelions (Taraxacum acaule, above) have beautiful flowers. It’s when the stalks going to seed rise above the lawn that the turf looks terrible. Sure, I worry what the neighbors think. But it only looks bad for a week or so. A lawn is not a natural state of vegetation—turfgrass is not native and woods and meadows are our natural flora—and so having weeds in it is purely an aesthetic objection. I can overcome this by learning to live with it. Really, controlling dandelions is not worth the risk and effort of the pesticides that so many people use.
On the other hand, plants that are invasive in natural areas have the capability of changing the kind of world we live in—reducing us from a diverse native forest to one that is degraded and less complex. Invasive species outcompete others; we risk living in a world where only the thugs have survived. That’s five-leaf akebia (Akebia quinata) above, reaching into powerlines.
Humans have introduced thousands of species to new habitats, either on purpose or by accident. This rate of introduction is orders of magnitude greater than what would occur naturally. A fraction of these have later been discovered to be invasive in their new habitat.
The introduction of species appears to bring new bounty to our landscape. But as Kim Todd writes in “Tinkering with Eden: A Natural History of Exotics in America” (Norton, 2001) there are unintended consequences. She writes about the introduction of non-native game species as one example: while these stories “. . . appear tales of addition, subtraction is the underlying theme . . . Instead of a world with heath hens and ring-neck pheasants, we have only ring-necked pheasants . . . Instead of a world with passenger pigeons and rock doves, we have only rock doves . . .” (p.252).
If we are successful controlling invasive plants on our preserves, our lands will be merely . . . less invaded. However, they will also be greater reserves of biodiversity. It is thankless work, this controlling invasives plants this summer (and every summer). People don’t tend to notice the absence of something like the increasingly ubiquitous mile-a-minute; they don’t know whether it hasn’t invaded here yet, or that we spend a great deal of effort keeping it from becoming established (the latter is true). But the stakes are high—either do what we can to minimize the impact of invasive species, or we’ll pass on to later generations a world that lacks many of the species we enjoy.